The problem isn't just open WiFi.
For $20 you can buy hardware to snoop on cell phone data (and voice) connections.
The encryption in GSM/GPRS/3G/4G/LTE is A5/1 which was cracked in 1999.
So yeah.. if you use the cell tower data connection on your phone/tablet/computer and think that is safer than WiFi it's only about $20-in-the-hands-of-an-attacker safer.
Edit: Oh, and VPN only moves the spying/hijacking problem somewhere else.